Other mistake: Murphy lands the helicopter on a railway line so an oncoming train will destroy it completely, and this happens exactly on cue with huge, dramatic explosions and flying debris. Apparently the train driver doesn't think this is important enough to interrupt his busy schedule - he doesn't stop the train. We do not hear brakes being applied - the wheels would make a noise like the sky coming down - and the train doesn't slow down at all - it just keeps on going.
Continuity mistake: When Dally falls off of his chair in the drive-in movie theater, you can hear Ponyboy's laughter above them all. When the shot changes to Cherry, you can see Ponyboy with a serious face on in the background but you can still hear him laughing.
Visible crew/equipment: About one hour and fifty minutes in, the two stars get into a fight and are rolling around the floor. In at least one scene, a cameraman, with a handheld Panavision camera, is quite visible in the middle of the shot.
Visible crew/equipment: When the first deal goes wrong and the man with the chainsaw jumps out the window you can clearly see him land on a grey crash mat because it lifts up at the corners. (00:27:55)
Visible crew/equipment: At one point Clint Eastwood is out in the woods practising his shooting with his new .44 auto-mag pistol. While he's doing this, a car pulls up and a black male begins to get out with a shotgun. (We later learn that this is his partner). As the man with the shotgun is opening his door, if you look at the reflection in the car window, you can clearly see the reflection of a man with a camera and another man standing next to him.
Continuity mistake: In the morgue, the trays containing medical tools change positions between shots. They are strategically moved further up the bodies for the closeup to conceal the genital area, whereas before they only covered the legs. (00:06:30 - 00:07:40)
Deliberate mistake: When Cletus is driving the Trans Am as the bandit, it shows him driving to the left and waving at a group of girls. The close up of him driving must be reversed because it looks like the Trans Am is now a right-hand drive. (00:26:45)
Visible crew/equipment: In one of the first scenes, two plain-clothes cops are chasing a suspect. The suspect runs through a house and down some stairs. Look under the stairs. You can see a person trying to hide in the dark under the stairs, presumably a stage hand.
Factual error: In one scene, our heroes go down a water slide with their bikes. Landing in the pool at the end would have made their walkie talkies unusable. But later they still work normally.